From: marshmellow42 <marshmellowrf@gmail.com>
Date: Tue, 10 Nov 2015 04:48:39 +0000 (-0500)
Subject: add checksum to viking demod
X-Git-Tag: v2.3.0~15^2~1
X-Git-Url: http://cvs.zerfleddert.de/cgi-bin/gitweb.cgi/proxmark3-svn/commitdiff_plain/3ea7254a57d1732e72f5d4b7bf21d1d6527faa19?ds=inline

add checksum to viking demod
---

diff --git a/common/lfdemod.c b/common/lfdemod.c
index 5d19c897..c8a2c69a 100644
--- a/common/lfdemod.c
+++ b/common/lfdemod.c
@@ -610,7 +610,10 @@ int VikingDemod_AM(uint8_t *dest, size_t *size) {
 	uint8_t preamble[] = {1,1,1,1,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
 	uint8_t errChk = preambleSearch(dest, preamble, sizeof(preamble), size, &startIdx);
 	if (errChk == 0) return -4; //preamble not found
-
+	uint32_t checkCalc = bytebits_to_byte(dest+startIdx,8) ^ bytebits_to_byte(dest+startIdx+8,8) ^ bytebits_to_byte(dest+startIdx+16,8)
+	    ^ bytebits_to_byte(dest+startIdx+24,8) ^ bytebits_to_byte(dest+startIdx+32,8) ^ bytebits_to_byte(dest+startIdx+40,8) 
+	    ^ bytebits_to_byte(dest+startIdx+48,8) ^ bytebits_to_byte(dest+startIdx+56,8);
+	if ( checkCalc != 0xA8 ) return -5;
 	if (*size != 64) return -5;
 	//return start position
 	return (int) startIdx;